The cryptographic signature guarantees the file is safe to install and was not tampered
with in any way.

That is due to blue light. Blue light from your phone and tablet screen is the visible light spectrum (380-550nm) for circadian regulation. According to the scientific studies, exposure to blue light imposes serious threats to retinal neurons and inhibits the secretion of melatonin, a hormone that influences circadian rhythms. It is proven that reducing blue light can greatly improve sleep.

Blue light filter is used to reduce blue light by adjusting the screen to natural color. Shifting your screen to night mode can relieve your eyes strain, and your eyes will feel at ease during night reading. Also blue light filter will protect your eyes and help you sleep easily.